For an explanation of a multiple computer system incorporating replicated shared memory reference is made to the present applicant's International Patent Application No. WO 2005/103926 (to which U.S. patent application Ser. No. 11/111,946 corresponds), and to International Patent Application No PCT/AU2005/001641 (WO2006/110,937) to which U.S. patent application Ser. No. 11/259,885 entitled: “Computer Architecture Method of Operation for Multi-Computer Distributed Processing and Co-ordinated Memory and Asset Handling” corresponds, and to Australian Patent Application No. 2005 905 582 (to which U.S. patent application Ser. No. 11/583,958 (60/730,543) and PCT/AU2006/001447 (WO2007/041762) correspond). For an explanation of partial or hybrid replicated shared memory, reference is made to the present applicant's co-pending application PCT/AU2007/00147 filed simultaneously herewith and claiming priority from Australian patent application No. 2006 905 534 entitled “Hybrid Replicated Shared Memory Architecture”, and to U.S. Patent Application No. 60/850,537 all of which are hereby incorporated by cross-reference for all purposes.
Briefly stated, the abovementioned patent specifications disclose that at least one application program written to be operated on only a single computer can be simultaneously operated on a number of computers each with independent local memory. The memory locations required for the operation of that program are replicated in the independent local memory of each computer. On each occasion on which the application program writes new data to any replicated memory location, that new data is transmitted and stored at each corresponding memory location of each computer. Thus apart from the possibility of transmission delays, each computer has a local memory the contents of which are substantially identical to the local memory of each other computer and are updated to remain so. Since all application programs, in general, read data much more frequently than they cause new data to be written, the abovementioned arrangement enables very substantial advantages in computing speed to be achieved. In particular, the stratagem enables two or more commodity computers interconnected by a commodity communications network to be operated simultaneously running under the application program written to be executed on only a single computer.
Prior art switch protocols rely upon a specific address for each message, which means that messages sent to some only of the computers of the multiple computer system must be sent sequentially, each message having a correspondingly different address. Alternatively, a broadcast message is sent to all computers and which contains the specific addresses of the computers constituting the subset of the computers to which the message is addressed. In these circumstances, computers receive messages which are not addressed to them and ignore those messages. Both arrangements are wasteful of bandwidth and constitute relatively inefficient communication arrangements.